Traditionally, machining of metal workpieces to produce desired articles, such as hobbing processes to produce spur and helical gears, shafts, splines, and the like, or face milling and face hobbing processes to produce bevel and hypoid gears, have been performed in the presence of a coolant medium supplied to the point of engagement of a tool and workpiece. Aside from the obvious function of cooling the tool and workpiece, coolant also reduces tool wear and serves to flush metal chips, which emanate from a machined workpiece, away from the area of engagement of tool and workpiece and out of the machine. Once flushed away from the tool and workpiece, chips may separated from the coolant by filtering or by magnetic separator means as is well known in the art.
While coolant certainly has many advantages, it also has its drawbacks. Coolant is expensive to purchase, and in some cases disposal costs are just as expensive. Coolant mist and coolant oil smoke are considered to be environmental hazards. Therefore, machines must include a mist/smoke collector as a means to remove such airborne contaminants from the atmosphere within the machine enclosure. Coolant circulation in a machine tool requires a pump and hoses to deliver coolant to the machining area, and a chip separator to remove metal chips from the coolant. Such separators are somewhat more complicated than simple powered drag lines used to convey dry chips. In some cases, filters may be needed to remove other debris from the coolant, or a coolant chiller may be required to control both the coolant and the machine equilibrium temperature.
Recently, dry machining processes such as dry hobbing of cylindrical gears and dry cutting of bevel gears have drawn attention as an alternative to processes utilizing coolant (wet machining processes). See, for example, Phillips, "New Innovations in Hobbing--Part II", Gear Technology, November/December 1994, pp. 26-30, and, Stadtfeld, "Gleason POWER-DRY-CUTTING.TM. of Bevel and Hypoid Gears", The Gleason Works, Rochester, N.Y., May 1997.
It may be seen that dry machining has the potential to overcome many serious and costly drawbacks associated with the use of a liquid coolant. Also, dry chips are normally more valuable as a recyclable material than chips which are residually wetted by a process fluid. Parts cut without coolant do not need washing, prior to further processing such as heat treatment.
However, the heat generated in dry machining processes is a contributor to tool wear and it also may have detrimental effects on the machine itself, causing differential growth of components such as spindles, bearings, or the machine frame. Much of the process heat in dry machining is removed by the chips that must be removed from the machine as quickly as possible and in a manner by which they do not contact the machine frame for any extended period of time.
One way to remove dry chips is to permit the hot chips to slide by gravity toward a chip conveyor built into the base of a hobbing machine. Such a chip removal system is shown in Ophey, "Gear Hobbing Without Coolant", Gear Technology, November/December 1994, pp. 20-24.
Another method of removing chips from a machine tool capable of wet and dry machining is known from U.S. Pat. No. 5,586,848 to Suwijn wherein the chips are discharged into the machine base where a reversible transfer mechanism carries them to respective wet or dry outlets.
Still another manner in which to remove chips from the machining interface and out of a machine is disclosed in commonly assigned and copending U.S. Pat. No. 5,951,219 to Stadtfeld et al. The generally circular-shaped shroud comprises a peripheral portion having a flange attached at one end thereof for securing the chip removal apparatus to a backing plate or directly to a machine tool. The other end of the peripheral portion is attached to a front portion made up of one or more sections that are arranged such that a tool and workpiece are provided appropriate space within the apparatus as is necessary to accommodate the angular separation between the tool and workpiece. The inner surface of the peripheral portion is curved, preferably circular, such that chips emanating from the tool-workpiece interface are projected toward the inner surface and travel along the curved surface into an outlet where they are conveyed away from the machine tool. The enclosure preferably further comprises means to project a gaseous stream along a portion of the inner surface of the apparatus for urging chips toward and/or into the outlet. Means to enhance air flow from the outlet may also be included.
It is an object of the present invention to provide a system to remove metal chips from a machine tool in a rapid manner such that heat from the chips is not transferred to the body of the machine tool.
It is a further object of the present invention to remove substantially all chips generated by a machining process from the machining chamber thus eliminating, or significantly reducing the frequency of, the need to manually remove chips that have escaped from the chip removal apparatus.